In the oil industry power tongs are used to either grasp and hold pipe while threaded joints are being made up, or to rotate pipe in order to make up such joints. In the past, power tongs have been provided with jaws that are mounted to swing about a pivot point in order to bring the jaw into bearing engagement against pipe. Jaws of these designs are constrained by upper and lower cage plates to which the jaws are connected.
Typically, several jaws, e.g. two opposed jaws, are advanced inwardly by rotating an outer encircling camming surface about a set of jaws with the pipe located at the center of rotation. This camming surface is typically formed on the inside of a C-shaped ring gear. Camming rollers on the jaws bear against this camming surface, causing the jaws to advance inwardly in response to the inward urging developed by the cam surface as it rotates past the camming rollers. When the jaws pivot about a pivot axis that is fixed in relationship to the cage plates, the path followed by the jaws as they are displaced inwardly is not perfectly radial. Rather the jaws approach the centrally mounted pipe for engagement following an arcuate path. Alternately, in some jaw designs the jaws advance radially towards the center of the tong.
It would be advantageous to provide a power tong of a simplified design that is more convenient to manufacture and which has a more extended camming surface. The present invention addresses that objective.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.